Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $173.34   12.400%   $194.8342   $194.83   $194.85   $194.80  
  Purchase #2 $183.43   9.753%   $201.3199   $201.32   $201.30   $201.30  
  Purchase #3 $178.83   11.126%   $198.7266   $198.73   $198.75   $198.70  
  Purchase #4 $117.61   5.866%   $124.509   $124.51   $124.50   $124.50  
  Purchase #5 $11.41   9.108%   $12.4492   $12.45   $12.45   $12.40  
  Purchase #6 $140.63   3.428%   $145.4508   $145.45   $145.45   $145.50  
  Purchase #7 $212.26   6.723%   $226.5302   $226.53   $226.55   $226.50  
  7 purchase totals = $1,017.51       $1,103.8199   $1,103.82   $1,103.85   $1,103.70